ESSENTIALS OF PHYSIOLOGY. 



are distributed to the inferior colliculus and internal geniculate body, 

 and thence to the temporal lobe of the cerebral hemisphere. 



The superior colliculus, on the other hand, is concerned with the 

 function of vision. It receives fibres from the optic tract, which 

 arborise round its nerve cells, and it gives origin to fibres which pass 

 to the nuclei of the third (oculo-motor) nerve. It is also connected by 



Optic nerve. 



. . Thalamus. 



External geni- 

 culate body. 



Superior 

 colliculus. 



Oculo-motor 

 nuclei. 



Optic radiation. 



Visuo-sensory 

 area. 



FIG. 23. Diagram showing the path of the visual impulses. 

 The oculo-motor nuclei are connected by commissural fibres (not shown in figure). 



a bundle of fibres, the superior brachium, with the external (lateral) 

 geniculate body. The optic tract ends in cell stations in the superior 

 colliculus, the external (lateral) geniculate body, and the thalamus 

 (fig. 23). From the two latter of these stations, other neurons carry 

 impulses to the cerebral cortex. The superior colliculus is also the 

 place of origin of the tecto-spinal fibres, which are found in the antero- 

 lateral column of the spinal cord. These cross in the mid-brain by the 

 fountain decussation of Meynert, and descend in the formatio reticularis 

 of mid-brain, pons, and medulla oblongata. 



